High temperature lasers such as the lead vapor and copper halide systems must operate as a sealed-off unit to maintain thermodynamic and thermochemical equilibrium conditions within the laser tubes. Under these circumstances the metal (halide) vapor pressure is controlled by the cold spot temperature. In addition, the chemical decomposition of the halide species is reversible, and long-lived operation of the laser tube can be realized. This requirement means that the entire inner surface of the laser tube must operate near the temperature required for adequate vapor pressure, which is 400.degree.-700.degree. C. for copper halides and approximately 1100.degree. C. for lead. Thus electrodes and electrical feedthroughs must be designed to withstand these high temperatures, and must also be capable of withstanding chemical attack at elevated temperatures by the laser tube contents. Even when the laser tube is not sealed off, the same electrode/feedthrough assemblies are required to prevent excessive condensation of the laser material near the electrical feedthrough.